package com.xiaoyu.lingdian.tool;

/**
 * CRC-CCITT 算法校验类
 */
public class CRCUtil {
	
	/**
	 * CCITT标准CRC16(1021)余数表 CRC16-CCITT ISO HDLC, ITU X.25, x16+x12+x5+1 多项式
	 * 高位在先时生成多项式 Gm=0x11021 低位在先时生成多项式，Gm=0x8408 本例采用高位在先
	 */
	private static int crc16_ccitt_table[] = { 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a,
			0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b,
			0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528,
			0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719,
			0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e,
			0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf,
			0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec,
			0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd,
			0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2,
			0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3,
			0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0,
			0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691,
			0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806,
			0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37,
			0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64,
			0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55,
			0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0 };

	/**
	 * 
	 * @param reg_init CRC校验时初值
	 * @param message 校验值
	 * @return
	 */
	private static int do_crc(int reg_init, byte[] message) {
		int crc_reg = reg_init;
		for (int i = 0; i < message.length; i++) {
			crc_reg = (crc_reg >> 8) ^ crc16_ccitt_table[(crc_reg ^ message[i]) & 0xff];
		}
		return crc_reg;
	}

	/**
	 * 根据数据生成CRC校验码
	 * 
	 * @param message
	 *            byte数据
	 * 
	 * @return int 返校验码
	 */
	public static int do_crc(byte[] message) {
		// 计算CRC校验时初值从0x0000开始。
		int crc_reg = 0x0000;
		return do_crc(crc_reg, message);
	}
	
	/**
	 * db44检验方法
	 * 
	 * @param message 消息内容
	 * @param crc 检验码值
	 * @return
	 */
	private static boolean do_crc(byte[] message,byte[] crc) {
		// 计算CRC校验时初值从0x0000开始。
		int crc_reg = 0x0000;
		int crc_value = (crc[0]&0xff)*256+(crc[1]&0xff);
		return crc_value ==do_crc(crc_reg, message);
	}
	
	/**
	 * 供db44结构代码使用,数组后两位为CRC-校验码值
	 * @param messages
	 * @return
	 */
	public static boolean do_crc_db44(byte[] messages) {
		// 计算CRC校验时初值从0x0000开始。
		byte[] messageArray = new byte[messages.length-2];
		byte[] crcArray = new byte[2];
		System.arraycopy(messages, 0, messageArray, 0, messageArray.length);
		System.arraycopy(messages, messages.length-2, crcArray, 0, 2);
		return do_crc(messageArray, crcArray);
	}

	public static void main(String[] args) {
		String str = "公司本部|19391199232.000000|2014-12-31|"
		+"手续费及佣金收入|18915399680.000000|2014-12-31|"
		+"手续费及佣金收入：经纪业务收入|10491599872.000000|2014-12-31|"
		+"投资收益|10311300096.000000|2014-12-31|"
		+"手续费及佣金收入：经纪业务收入：证券经纪业务收入|10192900096.000000|2014-12-31|"
		+"经纪业务|10177500160.000000|2014-12-31|"
		+"手续费及佣金收入：经纪业务收入：证券经纪业务收入：代理买卖证券业务|9068810240.000000|2014-12-31|"
		+"利息收入|7850809856.000000|2014-12-31|"
		+"证券投资业务|6759960064.000000|2014-12-31|"
		+"资产管理业务|6111309824.000000|2014-12-31|GRID5=2014-06-19|||1.50000000|2014-08-15|"
		+"2013-06-21|||3.00000000|2013-08-08|";

		// 一个db44测试样本数据
		byte p[] = str.getBytes();
		int crc = do_crc(p); // 计算前两位的CRC码
		// 65336
		System.out.println(crc);		
	}

}